In the manufacture of magnetic tapes and the like it is known to coat magnetic layers or stripes using a coating composition comprising dispersed magnetic particles, a binder polymer and an organic liquid. The coating is dried or cured by heating and is then calendered by passage through the nip of smooth calendering rolls. The latter operation increases the compactness of the magnetic layer and, therefore, its magnetic efficiency. It also improves the microsmoothness of the layer surface and reduces the noise in the reproduced signal.
Known processes for manufacturing magnetic cards suffer from various disadvantages. For example, in the silk-screening method of forming magnetic tracks described in U.S. Pat. No. 4,100,011, the magnetic particles tend to be oriented perpendicularly to the card surface. This reduces the frequency response of the recorded information.
Magnetic tracks can also be extruded on the support or deposited in grooves in the support and then calendered, as described in French Pat. No. 1,588,133 (corresponding to U.K. Pat. No. 1,180,356). A drawback of such methods is that the thickness and edge definition of the tracks are difficult to control. Furthermore, the organic liquids normally used for coating magnetic compositions, may attack the usual kinds of thermoplastic supports and distort their planarity.
The growing use of magnetic cards has led to continual searches for improvements. In particular, it is often desired to mask one or more magnetic tracks from view by covering such tracks with an opaque masking layer. Such masking is intended to strengthen coding inviolability and to protect the magnetic track against abrasion. The masking layer, however, must not excessively reduce the signal picked up by reading heads. The masking of magnetic tracks tends to reduce performance by increasing the spacing between the reading head and the track. This influence of head and track separation is well known.
The simultaneous maintenance of magnetic performance and improvement of inviolability constitute contradictory requirements that are difficult to meet, since the card usually comprises several tracks having unequal magnetic and geometric characteristics. The masking overcoat may unequally affect these characteristics.
Conceivably, tracks that are not coplanar could be concealed by a thick masking overcoat. However, a serious disadvantage would be that such a thick coating would reduce the magnetic efficiency of the recording article. In the present invention, the tracks can be concealed without serious loss of magnetic efficiency. An information-recording article such as a multitrack card can be masked with an opaque layer of minimum thickness which protects the card without causing excessive signal loss. This result can be achieved by using a novel element of this invention as an intermediate element in manufacturing such a card. The use of the intermediate element also permits the tracks to be deposited on a final support that is used in the information recording article without distorting such support. Often organic liquids (solvents or dispersant media) used for coating magnetic dispersions, distort the thermoplastic polymeric support that is normally used for a credit card or a bank card by dissolving or swelling it. As described herein, an element of this invention can be used as an intermediate element to prepare such a card and avoid the application of harmful solvents to the final support.